Surface coated impregnated waterleaf



Jan. 31, 1961 J. A. KLACSMANN 2,970,079

SURFACE COATED IMPREGNATED WATERLEAF Filed May 22, 1956 SURFACE COATINGCONSISTING ESSENTIALLY OF A PHENOL- FORMALDEHYDE RESIN AND POLYMERREACTION PRODUCT OF ACYRLONITRILE, AN ALPHA OLEFINIC CARBOXYLIC ACID ANDAN ESTER OF ALPHA OLEFINIC CARBOXYLIC ACID.

WEB OF POLYACRYLONITRILE FIBERS IMPREGNATED WITH A POLYMERIC REACTIONPRODUCT OF ACRYLONITRILE, AN ALPHA-OLEFINIC CARBOXYLIC ACID AND AN ESTEROF ALPHA-OLEFINIC CARBOXYLIC ACID.

INVENTOR JOHN ANTHONY KLACSMANN BY @YM AGENT United States Patent 6SURFACE COATED HVIPREGNATED WATERLEAF John Anthony Klacsmann, Newburgh,N.Y., assignor to E. I. du Pont de Nemours and Company, Wilmington,Del., a corporation of Delaware Filed May 22, 1956, Ser. No. 586,364

1 Claim. (Cl. 162-164) This invention relates to a novel article ofmanufacture and processes of making same. More particularly, it isrelated to a sheet or web of non-woven fibers having a binder ofpolymeric material distributed throughout.

This case is a continuation-in-part of my copending application SerialNo. 531,247, filed August 29, 1955, which is in turn acontinuation-in-part of Serial No. 523,605, filed July 21, 1955.

Both natural and synthetic fibers have been formed into batts or websand then impregnated with various resinous materials which serve as abinder for the fibers. Such products are not entirely satisfactory incertain fields Where high mechanical strength, abrasion resistance,electrical resistance and resistance to greases, oils, and organicliquid solvents are desired, such as, e.g., leather replacement, papers,structural elements, bearing seals and slot liners for motors andgenerators.

It is an object of this invention to provide a web of fibers boundtogether with an organic solvent-resistant polymeric material. A furtherobject is to provide a paper-like pellicle of a fibrous mass boundtogether with an organic solvent resistant polymer. A still furtherobject is to provide a leather-like product comprising a web ofpolyacrylonitrile fibers bound together with a polymeric materialintroduced into the web as an aqueous suspension. Other objects includeprocesses for preparing sheet materials ranging from paper-like productsto leather-like products.

These and other important objects are accomplished by impregnating a webof polyacrylonitrile fibers with an aqueous dispersion of the polymericreaction product of (A) acrylonitrile, (B) an alpha-olefinic carboxylicacid such as, e.g., acrylic acid, methacrylic acid, ethacrylic acid,phenyl acrylic acid, crotonic acid, maleic acid, itaconic acid andglutaconic acid and (C) an ester of one or more of the above mentioned(B) acids with a saturated aliphatic monohydric alcohol having 1 to 12carbon atoms. More specific objects are accomplished by surface coatingthe impregnated webs with a composition comprising the above describedpolymeric reaction product with or without other modifying resins.

By varying the composition of the copolymer impregnant as well as theratio of binder to fiber and the amount of heat and pressure applied tothe impregnated webs, it is possible to obtain products varying inproperties by varying the weight ratio of acrylonitrile to the ester ofalpha-olefinic carboxylic acid from 30:70 to 60:40.

The combined acrylonitrile and alpha-olefinic ester comprises from 85%to 98.5% and the alpha-olefinic carboxylic acid comprises 15% to 1.5% ofthe monomer mixture from which the polymer is derived. The percentagefigures are on a weight basis.

The acrylonitrile/alpha-olefinic ester ratio of the copolymer controlsor determines the mechanical strength, solvent resistance, outdoordurability and flexibility of the finished product. The alpha-olefiniccarboxyl'c rcid content of the copolymer stabilizes the dispersionagainst coagulation and aids in increasing solvent resistance and inadhering the copolymer to other materials. The ester of thealpha-olefinic carboxylic acid also aids in the coalescence of thepolymer particles.

The weight ratio of fiber to hinder may vary over a rather wide range,depending on the polymer composition, i.e., the weight ratio of binderto fiber can vary from 121.5 to 1:19.

In the case of polymers useful for still articles when using the lowerlimits of the acrylonitrile component of the copolymer, the alkyl groupof the ester of the alphaolefinic carboxylic acid is preferably derivedfrom a monohydric alcohol having v3 to 8 carbon atoms. When using theupper limits of the acrylonitrile content of the copolymer, it ispreferable to use a higher alkyl group on the ester, such as, e.g., an8-12 carbon atom alkyl group. The esters derived from methyl and ethylalcohol while useful tend to impart brittleness to the copolymer.

For the more flexible articles, when using the upper limits for theacrylonitrile content of the copolymer it is preferable to use an alkylester derived from monohydric alcohols having 8-12 carbon atoms. I

For more supple paper using the lower acrylonitrile content and theupper content of the ester of alphaolefinic carboxylic acid, it ispreferable to use the esters derived from monohydric alcohols having 4-8carbon atoms. It is also possible to use a blend of esters derived fromalcohols having an average carbon length of 4-8. In general, forflexible polymers the higher the acrylonitrile content of the copolymerthe greater the number of carbon atoms in the alcohol from which theesters are derived and vice versa.

The drawing is a side view illustration of theproduct of this inventionshowing a waterleaf impregnated throughout with a polymeric binder and asurface coating of a polymeric composition.

The following specific example represents the best mode contemplated forcarrying out the invention which is given by way of illustration and notlimitation. The parts and percentage figures are expressed on a weightbasis unless stated otherwise.

Example A dry paper sheet was prepared from V4" staple 3 denierpolyacrylonitrile fibers by preparing a .2% by weight fibrous slurry inwater in the'manner well known to those skilled in the art of papermaking. The-aqueous slurry was poured on a paper making screen and thewater was drained through the screen leaving a matted fibrous water leafdeposited thereon. The wet water leaf was pressed between two smoothrubber covered pressure rolls to remove excess water and smooth bothsurfaces. The water leaf was dried then impregnated with an aqueousresinous impregnating dispersion prepared from the following components:

Parts by wt. Polymerizale monomers:

Acrylonitrile 35.00 Butyl acrylate 60.00 Methacrylic acid 5.0

Polymerization initiator:

The excess composition was allowed to drain from the water leaf andthenpressed'between two smooth rubber lites BR.15,100) 3.0 28.%-ammoniumhydroxide 0.5 Water. 34.8

The: coated paperwas driedafter each dip coat by forced drying at 250 F.The paper was passed through the dip bath at a rate of l yardper minute.The surface coating onthe paper was heat cured by passing between heatedrevolvingsteel belts under 50-pisi. at" 340 F. for a dwell of threeminutes.

The finished product had'the following'weiglitspecifications andphysicalproperties:

Weightspecifications: v

Total 4.50 oz./s q. yd. Weight of fiber 2. l8{oz./sq. yd. Weightpolymer-in paper beiore'ceating .32 ozJsq. yd. I Weight'coating onpaper. 2;00'oz./sq:yd'. Total weight of polymer.- 2.32 oa/sg: yd-.iTotal weight of fiber 2.18 oZ./sq.1yd. Physical properties:

Dielectric strength 650-volts/mil;-thiekness.-

Tensile strength (strip 1 wide)- Machine direction Trans-machinedirection Crease tensile strength (strip 1 W1 Machine directionTrans-machine direction; 25 lbs; at crease. Elmendorf tear strength-Machine direction -l 15 scale readings.

Trans-machine direction scale readings.

Thecoated paper described above is particularly use fulias an electricalinsulation intthepresence 'of a hydro-" carbonlubricating-oil.and arefrigerantof the class con sisting of chloroalkanes,chlorofluoroalkanesandabromoalkanes. There is a tendency forobjectionable copper plating to occur in some refrigeration systems whenthere is :used therein refrigerants.of-therclassvset forth'above/ The"product of the above: described I example; com prisingpolyacrylonit-rilel fibers, abinder and" a :sur facecoating containing apolymer derived from acrylonitrile is very efiective'tomateiiallyinhibit or delay such objectionable copperplating: if the: refrigerantand the oil are brought'a'into contact therewith OOHtiHHOUSlYTOIIintermittently at frequent intervals: during; suchopera tions.: Theprecise mechanism through. which such-polymericmateiialsso function isnot known.

Fora more'det'ailed descripti'ohof the preparation of an aqueouscopolymer impregnating dispersions of this invention, reference is madeto copending application Serial No. 369,890, filed July 23, 1953, byJames J. Sanderson.

While there are above disclosed but a limited numberof embodiments ofthe structure,processandproduct of"tlfeiiiveiition herein presented; itis possible to pro duoe still otherembodiments without departingfro'mthe inventive"concept'here'in disclosedpa'n'd it is'de'sirdtherefore that only such limitations be imposd oh-'the"appendedclaimasare'stated therein; orrequired by the prior art. N v

The embodiments'ofthe invention-in which an exclusive property orprivilege is claimed are defined as follows.

I claim: I

A coated water-leaf comprising a sheet of polyacrylonitrilefibersuniformly impregnated throughout with a binder comprising the polymericreaction product of a mixture of monomerscomprising (A) acrylonit rile,(B) an alphaolefiiiic carboxylic acid selected fromthe class; consistingof acrylic, methacrylic, ethacrylic, phenyl acrylic; crotonic, itaconic,glutaconic, and maleic; and ('C an ester of said alpha-olefiniccarboxylic acids and a-saturated aliphaticmo'nohydric alcoholhaving l-12carbon atoms; the weight ratio of (A) to (C) b eingiwithin the range30570 to :40, and (B)' beingfpresent in an amount corresponding to 1.5%to 15 %*ofthe total weight of said monomer mixture, saidimpregnated'sheet surface coated with a compositionconsistingessentially-of saidfpolymeric reaction product and aphenol-formaldehyde resin.

